Pneumatic tire

Abstract

A pneumatic tire is provided that exhibits good sealing performance regardless of temperature conditions. In a pneumatic tire where a sealant layer (10) composed of an adhesive sealant material is provided on the inner surface of the tread (1), the thickness of the sealant layer (10) at 0°C is defined as G0, and the thickness of the sealant layer (10) at 50°C is defined as G... 50 The width of the sealant layer (10) at 0℃ is set to W0, and the width of the sealant layer (10) at 50℃ is set to W. 50 At that time, the thickness change rate R will be expressed by the following formula (1). G The width change rate R is set to below 3% and will be expressed by the following formula (2). W Set to below 3%. G =(|G 50 -G0| / G0)×100(1)R W =(|W 50 -W0| / W0)×100(2).

Description

Technical Field

[0001] This invention relates to a self-sealing pneumatic tire having a sealant layer on the inner surface of the tire. Background Technology

[0002] In pneumatic tires, a solution has been proposed to provide a sealant layer on the radially inner side of the inner liner of the tread (for example, see Patent Document 1). In such a pneumatic tire, when a foreign object such as a nail is embedded in the tread, the sealant material constituting the sealant layer flows into its through-hole, which can suppress the decrease in air pressure and maintain driving.

[0003] In the aforementioned self-sealing pneumatic tires, if the sealant material has a low viscosity, improved sealing performance can be expected due to its ease of flow into the through-holes. However, due to the added heat and centrifugal force during driving, the sealant material flows towards the center of the tire. Consequently, if the through-holes are located away from the central area of ​​the tire, insufficient sealant material may result, potentially leading to inadequate sealing. On the other hand, if the sealant material has a high viscosity, the aforementioned flow can be prevented, but the sealant material may have difficulty flowing into the through-holes, potentially reducing sealing performance. Therefore, when a sealant layer is applied to the inner surface of the tire, a good balance must be struck between suppressing the flow of sealant material during driving and ensuring good sealing performance.

[0004] In addition, sealant materials are generally based on rubber, and therefore tend to change in volume with temperature. That is, sealant materials tend to expand at high temperatures and shrink at low temperatures. Furthermore, the viscosity of sealant materials is also temperature-dependent, thus their flowability changes with temperature. That is, if the viscosity of the sealant material decreases at high temperatures, the sealant material will flow, and the thickness and width of the sealant layer may change. Due to such dimensional changes in the sealant layer, for example, if the thickness of the sealant layer decreases, a sufficient amount of sealant material may have difficulty flowing into the through-holes; if the width of the sealant layer decreases, the area where sealing performance can be achieved may become smaller. Tires can be used in a wide variety of environments (cold regions, hot regions, regions with large diurnal temperature ranges, regions with large annual temperature ranges, etc.). Furthermore, since large temperature changes can occur depending on driving speed, when setting sealant layers in tires, efforts are made to suppress dimensional changes in the sealant layer (sealant material) caused by temperature variations, so as to maintain good sealing performance regardless of temperature conditions.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-152110 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The purpose of this invention is to provide a pneumatic tire with a sealant layer on the inner surface of the tire, which can maintain good sealing performance regardless of temperature conditions.

[0010] Technical solution

[0011] The pneumatic tire of the present invention, which achieves the above-mentioned objective, comprises: a tread portion extending in a ring shape along the tire circumference; a pair of sidewall portions disposed on both sides of the tread portion; and a pair of bead portions disposed inside the tire outer diameter direction of these sidewall portions. A sealant layer made of an adhesive sealant material is provided at least on the inner surface of the tread portion. The pneumatic tire is characterized in that, when the thickness of the sealant layer at 0°C is defined as G0, and the thickness of the sealant layer at 50°C is defined as G... 50 The width of the sealant layer at 0°C is set as W0, and the width of the sealant layer at 50°C is set as W... 50 At that time, the thickness change rate R is expressed by the following formula (1). G For width changes of less than 3%, the following formula (2) represents the rate of change R. W It is below 3%.

[0012] R G =(|G 50 -G0| / G0)×100 (1)

[0013] R W =(|W 50 -W0| / W0)×100 (2)

[0014] Invention Effects

[0015] As described above, the pneumatic tire of the present invention achieves sealing performance by having a sealant layer; however, as described above, the thickness variation rate R is set sufficiently low. G and width change rate R W Therefore, even with temperature changes, dimensional changes are not easily caused, and excellent sealing performance can be maintained regardless of temperature conditions.

[0016] It should be noted that "thickness change rate R" G"Calculated using the above formula (1), specifically, the following method is used. That is, at each of the twelve equal divisions of the inner circumference of the tire, the equator position of the tire and three positions 10mm inside the tire width direction from both ends of the sealant layer are set as measurement points. At each measurement point, a needle with a diameter of 0.5mm is vertically inserted into the sealant layer. When the tip of the needle reaches the interface between the sealant layer and the inner surface of the tire, the position of the needle corresponding to the surface of the sealant layer (the surface on the inner side of the tire cavity) is marked, and the length from the tip of the needle pulled out of the sealant layer to the aforementioned mark (the thickness of the sealant layer) is measured. "Thickness of the sealant layer at 0℃ G0" and "Thickness of the sealant layer at 50℃ G 50 "Measurements were taken after setting the tire's ambient temperature to its respective conditions (0°C or 50°C) and allowing it to stand for one hour. The values ​​of G0 and G at each measurement point were then calculated." 50 The difference (|G) 50 -G0|), the value of the measurement point with the largest difference is set as the "thickness change rate R". G Similarly, "width change rate R" W "Calculated using the above formula (2), but specifically, it is obtained using the following method. That is, the inner circumference of the tire is divided into twelve equal parts as measurement points, and at each measurement point, the length (width of the sealant layer) between the two ends of the sealant layer along the tire width direction is measured. "Width of the sealant layer at 0℃ W0" and "Width of the sealant layer at 50℃ W 50 "Measurements were taken after setting the tire's ambient temperature to its respective conditions (0°C or 50°C) and allowing it to stand for one hour. The values ​​of W0 and W at each measurement point were then calculated." 50 The difference (|W) 50 -W0|), set the value of the measurement point with the largest difference as "width change rate R" W ".

[0017] In this invention, the viscosity η0 (unit: kPa·s) of the adhesive sealant material at 0°C is preferably the same as the viscosity η of the adhesive sealant material at 50°C. 50 The ratio η0 / η (unit: kPa·s) 50 The viscosity is 6 or lower. Setting the viscosity in this way improves sealing performance. In particular, the viscosity change with temperature is moderately small, thus ensuring excellent sealing performance regardless of temperature conditions. It should be noted that the viscosity of the adhesive sealant material is a value measured using a rotational viscometer at the specified temperature conditions (0°C, 50°C) according to JIS K6833-1:2008.

[0018] In this invention, the adhesive sealant material is preferably cross-linked. In this way, by forming the sealant layer from a pre-cross-linked adhesive sealant material, it is advantageous to prevent deformation of the sealant layer in both the tire width and tire circumferential directions.

[0019] In this invention, it is preferable that the proportion A of toluene-insoluble matter, expressed by the following formula (3), in the adhesive sealant material is 30% to 60% by mass. Such an adhesive sealant material has a moderate crosslinking density and small dimensional changes with temperature, thus facilitating excellent sealing performance regardless of temperature conditions.

[0020] A = (M2 / M1) × 100 (3)

[0021] (In the formula, M2 is the mass of the toluene-insoluble residue remaining after the adhesive sealant material is immersed in toluene and left for one week [unit: g], and M1 is the initial mass of the adhesive sealant material before it is immersed in toluene [unit: g])

[0022] In this invention, it is preferable to mix a crosslinking agent containing sulfur into the adhesive sealant material. This results in good adhesion of the adhesive sealant material to the inner surface of the tire, which helps prevent deformation of the sealant layer in the tire width and circumferential directions (flow of the adhesive sealant material).

[0023] In this invention, the rubber component constituting the adhesive sealant material preferably includes butyl rubber. By mixing butyl rubber in this way, the adhesion of the adhesive sealant material to the inner surface of the tire can be improved, which helps to ensure good sealing performance.

[0024] In this invention, it is preferable to provide an auxiliary sheet covering the surface of the sealant layer. By providing the auxiliary sheet in this way, deformation of the sealant layer is restricted, thus helping to suppress deformation and flow of the sealant layer. Furthermore, it also prevents foreign matter from adhering to the surface of the sealant layer.

[0025] It should be noted that, in the following description, the tire dimensions are determined with the tire rim assembled on a standard rim, inflated to the standard internal pressure, and subjected to the standard load. "Standard rim" refers to the rim specified for each tire in a specification system that includes tire reference specifications. For example, JATMA is designated as a standard rim, TRA as a "Design Rim," or ETRTO as a "Measuring Rim." "Standard internal pressure" refers to the air pressure specified for each tire in a specification system that includes tire reference specifications. For JATMA, it is the maximum air pressure; for TRA, it is the maximum value listed in the table "Tire Load Limits at Various Cold Inflation Pressures"; and for ETRTO, it is the "Inflation Pressure," but for passenger car tires, it is set to 180 kPa. "Regular load" refers to the load specified for each tire in the specification system, which includes tire reference specifications. For JATMA, it is set as the maximum load capacity; for TRA, it is set as the maximum value recorded in the table "Tire Load Limits ATVARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is set as "Load Capacity". However, when the tire is for passenger cars, it is set as 88% of that load. Attached Figure Description

[0026] Figure 1 Meridional cross-sectional view showing an example of the pneumatic tire of the present invention.

[0027] Figure 2 Meridional cross-sectional view showing another example of the pneumatic tire of the present invention. Detailed Implementation

[0028] Hereinafter, the structure of the present invention will be described in detail with reference to the accompanying drawings.

[0029] For example, such as Figure 1 As shown, the pneumatic tire (self-sealing pneumatic tire) of the present invention comprises: a tread portion 1 extending in the circumferential direction of the tire to form an annular shape; a pair of sidewall portions 2 disposed on both sides of the tread portion 1; and a pair of bead portions 3 disposed radially inside the sidewall portions 2. Figure 1 In the attached diagram, the symbol CL indicates the tire equator. It should be noted that... Figure 1This is a radial cross-sectional view, so it is not depicted, but the tread portion 1, sidewall portion 2, and bead portion 3 extend circumferentially along the tire to form a ring, thus constituting the basic ring-shaped structure of a pneumatic tire. In addition, unless otherwise specified, other tire components in the radial cross-sectional view also extend circumferentially along the tire to form a ring.

[0030] exist Figure 1 In this example, a carcass layer 4 is mounted between a pair of left and right bead portions 3. The carcass layer 4 includes multiple reinforcing cords extending radially along the tire, which are folded back from the inside of the vehicle to the outside around the bead core 5 and the sidewall core 6 disposed in each bead portion 3. The sidewall core 6 is disposed on the outer periphery of the bead core 5 and is covered by the main body and folded-back portion of the carcass layer.

[0031] Multiple layers are embedded on the outer periphery of the carcass layer 4 of the tread portion 1. Figure 1 The belt layer 7 consists of two layers. Among these multi-layered belt layers 7, the layer with the smallest belt width is called the smallest belt layer 7a, and the layer with the largest belt width is called the largest belt layer 7b. Each belt layer 7 includes multiple reinforcing cords inclined relative to the tire circumference, and the reinforcing cords are arranged to intersect each other between layers. The inclination angle of the reinforcing cords relative to the tire circumference in these belt layers 7 is set, for example, in the range of 10° to 40°. A belt reinforcement layer 8 is provided on the outer periphery of the belt layer 7 in the tread portion 1. In the illustrated example, two belt reinforcement layers 8 are provided: a full cover layer covering the entire width of the belt layer 7 and an edge cover layer disposed on the outer periphery of the full cover layer, covering only the ends of the belt layer 7. The belt reinforcement layer 8 includes organic fiber cords oriented along the tire circumference, the angle of which relative to the tire circumference is set, for example, 0° to 5°.

[0032] In the tread portion 1, a tread rubber layer R1 is disposed on the outer periphery of the aforementioned tire components (carcass layer 4, belt layer 7, and belt reinforcement layer 8). The tread rubber layer R1 may have a structure in which two rubber layers (crown layer and base tread layer) with different physical properties are stacked along the radial direction of the tire. A sidewall rubber layer R2 is disposed on the outer periphery (outer side in the tire width direction) of the carcass layer 4 in the sidewall portion 2, and a rim cushion rubber layer R3 is disposed on the outer periphery (outer side in the tire width direction) of the carcass layer 4 in the bead portion 3.

[0033] An inner liner 9 is provided along the tire carcass layer 4 on the inner surface of the tire. This inner liner 9 is a layer used to prevent air filled inside the tire from permeating to the outside of the tire. The inner liner 9 is, for example, composed of a rubber composition mainly composed of butyl rubber, which has air-permeable properties. Alternatively, it may be composed of a resin layer with a thermoplastic resin as a matrix. In the case of a resin layer, it may be a resin layer in which elastomer components are dispersed in a thermoplastic resin matrix.

[0034] This invention relates to providing a sealant layer 10, described later, on the inner surface of such a pneumatic tire. Therefore, the basic structure of the pneumatic tire of this invention is not limited to the structure described above, as long as it includes the sealant layer 10. It should be noted that the sealant layer 10 refers to a layer adhered to the inner surface of a pneumatic tire having the basic structure described above. Specifically, the sealant layer 10 is provided in areas where foreign objects such as nails may puncture during driving, that is, on the inner surface of the tire (the radially inner side of the inner liner 9) corresponding to the contact area of ​​the tread portion 1. Furthermore, when a foreign object such as a nail punctures the tread portion 1, the sealant layer 10, by allowing the sealant material constituting the sealant layer 10 to flow into its through-holes and sealing the through-holes, can suppress the decrease in air pressure and maintain driving stability.

[0035] Regarding the sealant layer 10 of the present invention, if the thickness at 0°C is defined as G0 and the thickness at 50°C is defined as G... 50 The sealant layer 10 of the present invention has the following characteristics: the thickness change rate R, expressed by the following formula (1), is... G The content should be below 3%, preferably below 2%. It should be noted that G0 and G... 50 The only difference is the temperature measured, but the measurement sites are the same. Therefore, in the figure, G0 and G are represented by [missing information]. 50 The reference numerals in both figures indicate the thickness G. The thickness variation rate R is set sufficiently low in this way. G Therefore, even with temperature changes, dimensional changes (thickness changes) are not easily caused. Regardless of temperature conditions, the amount of sealant material flowing into the through hole can be fully ensured, resulting in excellent sealing performance.

[0036] R G =(|G 50 -G0| / G0)×100 (1)

[0037] At this point, if the thickness change rate R G If the thickness exceeds 3%, then when the thickness of the sealant layer 10 becomes small, it is impossible to sufficiently ensure the amount of sealant material flowing into the through hole, and the sealing performance cannot be well maintained. The thickness of the sealant layer 10 is not particularly limited; in typical pneumatic tires, a thickness G of 0.5 mm to 5.0 mm is preferred. It should be noted that the thickness of the sealant layer 10 described herein is related to G0 and G... 50 The thickness is different, being the thickness at room temperature (25°C). This thickness ensures good sealing while suppressing sealant flow during driving. Furthermore, it provides good processability when adhering the sealant layer 10 to the inner surface of the tire. If the thickness of the sealant layer 10 is less than 0.5 mm, it is difficult to ensure adequate sealing. If the thickness of the sealant layer 10 exceeds 5.0 mm, the tire weight increases, and rolling resistance deteriorates.

[0038] Furthermore, regarding the thickness of the sealant layer 10, if the thickness at -30°C is set as G... -30 Let the thickness at 80℃ be G. 80 The thickness variation rate R of the sealant layer 10 of the present invention, expressed by the following formula (1'), is... G Preferably, it is 3% or less, more preferably 2.5% or less. If the thickness variation rate R is set sufficiently small in this way... G Therefore, even with significant temperature changes, dimensional changes (thickness changes) are not easily observed. Regardless of temperature conditions, the amount of sealant material flowing into the through-hole is sufficiently guaranteed, further enhancing excellent sealing performance. It should be noted that G... -30 G 80 R G 'It is possible to change only the temperature conditions and use them with G0, G 50 R G The same method can be used to find it.

[0039] R G '=(|G 80 -G -30 | / G -30 )×100 (1')

[0040] Similarly, regarding the sealant layer 10 of the present invention, if the width at 0°C is set to W0 and the width at 50°C is set to W... 50 The sealant layer 10 of the present invention has the following characteristics: the width variation rate R expressed by the following formula (2) W The content should be 3% or less, preferably 2% or less. It should be noted that W0 and W... 50 The only difference is the temperature measured, but the measurement sites are the same. Therefore, in the figure, W0 and W are represented by [missing information]. 50 The reference numerals in both figures indicate the thickness W. The width variation rate R is set sufficiently low in this way. W Therefore, even with temperature changes, dimensional changes (width changes) are not easily caused, and the area that can fully perform its sealing function can be fully guaranteed regardless of temperature conditions, thus achieving excellent sealing performance.

[0041] R W =(|W 50 -W0| / W0)×100 (2)

[0042] At this point, if the width change rate R WIf the width exceeds 3%, when the width of the sealant layer 10 becomes smaller, it is not possible to adequately ensure the area covered by the sealant layer 10 (the area that can perform sealing), and the sealing performance cannot be well maintained. The width of the sealant layer 10 is not particularly limited, but in general pneumatic tires, it is preferable that the width of the sealant layer 10 is greater than or equal to the width Wb of the belt layer 7 (the width of the widest belt layer (in the illustrated example, the maximum belt layer 7b)). Furthermore, the protrusion w of the sealant layer 10 from the normal line of the carcass line passing through the end of the widest belt layer (in the illustrated example, the maximum belt layer 7b) in the width direction is preferably within 20 mm. It should be noted that the width and protrusion w of the sealant layer 10 described herein are related to W0 and W... 50 The dimensions are different, and are for room temperature (25°C).

[0043] Furthermore, regarding the width of the sealant layer 10, if the width at -30℃ is set as W... -30 Set the width of 80° to W. 80 The width variation rate R of the sealant layer 10 of the present invention, expressed by the following formula (2'), is... W Preferably, it is 3% or less, more preferably 2.5% or less. If the width variation rate R is set sufficiently small in this way... W Therefore, even with significant temperature changes, dimensional changes (width changes) are not easily observed. Regardless of temperature conditions, the amount of sealant material flowing into the through-hole is sufficiently guaranteed, further enhancing excellent sealing performance. It should be noted that W... -30 W 80 R W 'It is possible to change only the temperature conditions and use them with W0 and W' 50 W G The same method can be used to find it.

[0044] R W '=(|W 80 -W -30 | / W -30 )×100 (2')

[0045] The sealant layer 10 can be formed by subsequently bonding an adhesive sealant material (hereinafter referred to as "sealant material") to the inner surface of a vulcanized pneumatic tire. For example, the sealant layer 10 can be formed by bonding a sheet-shaped sealant material to the entire circumference of the inner surface of the tire, or by bonding a rope-shaped or strip-shaped sealant material spirally to the inner surface of the tire. In this case, a cross-linked sealant material is preferred. Using a pre-cross-linked sealant material in this way can more effectively prevent deformation of the sealant material in the tire width direction and tire circumferential direction.

[0046] From the viewpoint of suppressing deformation of the sealant layer 10, such as Figure 2 As shown, an auxiliary piece 11 covering the surface of the sealant layer 10 can be further provided on the surface of the sealant layer 10 (the surface exposed to the inner cavity of the tire). Figure 2 In addition to auxiliary piece 11, it has the same Figure 1 The same structure. If such an auxiliary piece 11 is present, the deformation (flow of sealant material) of the sealant layer 10 is restricted, which helps prevent deformation of the sealant material in the tire width and circumferential directions. Furthermore, by providing the auxiliary piece 11, foreign matter can also be prevented from adhering to the surface of the sealant layer 10. The material of the auxiliary piece 11 is not particularly limited, but resin films such as polyethylene and polyamide are preferred. The auxiliary piece 11 mainly suppresses the deformation of the sealant layer 10 as described above, therefore it does not need to cover the entire surface of the sealant layer 10; for example, it can be a raw material with localized holes or gaps, such as a mesh or wire mesh. Furthermore, if the auxiliary piece 11 is a sheet without holes or gaps, it does not need to cover the entire surface of the sealant layer 10, but covering at least 80%, preferably more than 90%, of the surface area of ​​the sealant layer 10 (the area of ​​the surface exposed to the tire cavity) is preferable.

[0047] In this invention, common materials can be used as sealant materials for the sealant layer 10 of a self-sealing pneumatic tire. However, from the viewpoint of suppressing deformation of the sealant layer 10 due to temperature changes, it is preferable to use a viscosity η0 (unit: kPa·s) at 0°C and a viscosity η at 50°C. 50 The ratio η0 / η (unit: kPa·s) 50 The sealant material with a viscosity of 6 or less, and more preferably 4 or less, is preferred. Using a sealant material with such properties improves sealing performance. In particular, the viscosity changes little with temperature, thus providing excellent sealing performance regardless of temperature conditions. In this case, if the viscosity ratio η0 / η 50 If the value exceeds 6, the processability of the sealant material may decrease. Viscosity η0 and viscosity η 50 There are no particular limitations, but from the point of view of the basic properties of a sealant material (ensuring good sealing performance while not flowing easily during operation), it is preferable to set the viscosity η0, for example, to be 2 kPa·s to 100 kPa·s.

[0048] Furthermore, regarding the viscosity of the sealant material, if the viscosity at -30°C is set as η... -30 [Unit: kPa·s], let the viscosity at 80℃ be η. 80 When [unit: kPa·s], the ratio η of these is... -30 / η 80 Preferably, the viscosity is 18 or less, more preferably 12 or less. Furthermore, the viscosity η... 80For example, a viscosity setting of 0.5 kPa·s to 30 kPa·s is preferable. By setting the viscosity in this way, even with significant temperature changes, the viscosity change is moderately small, thus ensuring excellent sealing performance regardless of temperature conditions. It should be noted that the viscosity η... -30 η 80 It is possible to change only the temperature conditions while using the viscosity η0, η 50 The same method can be used to find it.

[0049] Furthermore, the sealant material used in this invention preferably has the following characteristics: the proportion A of toluene-insoluble matter, represented by the following formula (3), is 30% to 60% by mass, preferably 35% to 50% by mass.

[0050] A = (M2 / M1) × 100 (3)

[0051] (In the formula, M2 is the mass of the toluene-insoluble residue remaining after the sealant material is immersed in toluene and left for one week [unit: g], and M1 is the initial mass of the sealant material before immersion in toluene [unit: g])

[0052] Sealant materials with these properties are advantageous in maintaining excellent sealing performance regardless of temperature conditions. Specifically, by setting the proportion of toluene-insoluble matter A to 30%–60% by mass, a good crosslinking density is achieved, thus imparting a property of minimal dimensional change with temperature variations, resulting in excellent sealing performance regardless of temperature conditions. If the proportion of toluene-insoluble matter A is less than 30% by mass, the crosslinking density is low, and the effect of suppressing dimensional change with temperature variations cannot be fully achieved. If the proportion of toluene-insoluble matter A exceeds 60% by mass, the crosslinking density is too high, and the sealing performance may decrease.

[0053] The specific mixing of the sealant materials used in this invention is not particularly limited as long as they possess the aforementioned properties. However, in order to reliably obtain the aforementioned properties, the sealant materials used in this invention are preferably composed, for example, of the sealant material composition described later.

[0054] In the sealant material composition constituting the sealant material of the present invention (hereinafter referred to as "the sealant material composition of the present invention"), it is preferable that the rubber component includes butyl rubber. The proportion of butyl rubber in the rubber component is preferably 10% by mass or more, more preferably 20% to 90% by mass. By including butyl rubber in this way, good adhesion to the inner surface of the tire can be ensured. If the proportion of butyl rubber is less than 10% by mass, adhesion to the inner surface of the tire cannot be sufficiently ensured.

[0055] In the sealant material composition of the present invention, halogenated butyl rubber is preferably included as a butyl rubber. Examples of halogenated butyl rubber include chlorinated butyl rubber and brominated butyl rubber, with chlorinated butyl rubber being particularly preferred. When using chlorinated butyl rubber, the proportion of chlorinated butyl rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass to 85% by mass. By including halogenated butyl rubber (chlorinated butyl rubber), the reactivity of the rubber component with the crosslinking agent and organic peroxide described later is improved, which is beneficial for balancing ensuring sealing and inhibiting sealant flow. In addition, the processability of the sealant material composition is also improved. If the proportion of chlorinated butyl rubber is less than 5% by mass, the reactivity of the rubber component with the crosslinking agent and organic peroxide described later is not sufficiently improved, and the desired effect cannot be fully obtained.

[0056] In the sealant material composition of the present invention, it is not necessary for the entire amount of butyl rubber to be halogenated butyl rubber (chlorinated butyl rubber); non-halogenated butyl rubber may also be used in combination. Examples of non-halogenated butyl rubber include unmodified butyl rubber commonly used in sealant material compositions, such as BUTYL-065 manufactured by JSR Corporation and BUTYL-301 manufactured by LANXESS Corporation. When halogenated and non-halogenated butyl rubbers are used in combination, the amount of non-halogenated butyl rubber mixed in 100% by mass of the rubber component is preferably less than 20% by mass, more preferably less than 10% by mass.

[0057] In the sealant material composition of the present invention, it is preferable to use two or more rubbers as butyl rubbers. That is, it is preferable to use chlorinated butyl rubber in combination with other halogenated butyl rubbers (e.g., brominated butyl rubber) or non-halogenated butyl rubbers. Since the vulcanization rates of chlorinated butyl rubber, other halogenated butyl rubbers (brominated butyl rubber), and non-halogenated butyl rubber are different, if at least two are used in combination, the physical properties (viscosity, elasticity, etc.) of the vulcanized sealant material composition will not be homogeneous due to the different vulcanization rates. That is, due to the distribution (concentration unevenness) of rubbers with different vulcanization rates within the sealant material composition, relatively hard and relatively soft portions are mixed together in the vulcanized sealant layer. As a result, flowability is suppressed in the relatively hard portions, while sealing performance is achieved in the relatively soft portions, which is beneficial for achieving a good balance of these properties.

[0058] In the sealant material composition of the present invention, other diene rubbers besides butyl rubber may also be mixed as the rubber component. Other diene rubbers that can be used include: natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), nitrile rubber (NBR), and other rubbers commonly used in sealant material compositions. These other diene rubbers can be used alone or in arbitrary mixtures.

[0059] In the sealant material composition of the present invention, a crosslinking agent is preferably incorporated. It should be noted that "crosslinking agent" in the present invention refers to a crosslinking agent from which organic peroxides have been removed, such as sulfur, zinc oxide, cyclic sulfides, resins (resin vulcanization), amines (amine vulcanization), etc. As a crosslinking agent, a crosslinking agent containing sulfur (e.g., sulfur) is particularly preferred. By incorporating a crosslinking agent in this way, a suitable amount of crosslinking can be achieved to balance ensuring sealing and preventing sealant flow. The amount of crosslinking agent incorporated is preferably 0.1 to 40 parts by weight, more preferably 0.5 to 20 parts by weight, relative to 100 parts by weight of the aforementioned rubber component. If the amount of crosslinking agent incorporated is less than 0.1 parts by weight, it is essentially the same as not containing a crosslinking agent, and proper crosslinking cannot be achieved. If the amount of crosslinking agent incorporated exceeds 40 parts by weight, the crosslinking of the sealant material composition is excessive, and the sealing performance is reduced.

[0060] In the sealant material composition of the present invention, the aforementioned crosslinking agent is not used alone, but preferably in combination with an organic peroxide. By combining the crosslinking agent and the organic peroxide in this way, a suitable amount of crosslinking can be achieved to balance ensuring sealing and preventing sealant flow. The amount of organic peroxide mixed relative to 100 parts by weight of the aforementioned rubber component is preferably 1 to 40 parts by weight, more preferably 1.0 to 20 parts by weight. If the amount of organic peroxide mixed is less than 1 part by weight, there is too little organic peroxide, and sufficient crosslinking cannot be achieved, thus failing to obtain the desired physical properties. If the amount of organic peroxide mixed exceeds 40 parts by weight, the crosslinking of the sealant material composition is excessive, resulting in reduced sealing performance.

[0061] When using a crosslinking agent and an organic peroxide in this manner, it is preferable to set the mass ratio A / B of the crosslinking agent mixture A to the organic peroxide mixture B to be 5 / 1 to 1 / 200, more preferably 1 / 10 to 1 / 20. By setting such a mixing ratio, a better balance can be achieved in ensuring sealing and preventing sealant flow.

[0062] Examples of organic peroxides include: dicumyl peroxide, tert-butylcumyl peroxide, benzoyl peroxide, butyl hydroperoxide, p-chlorobenzoyl peroxide, and 1,1,3,3-tetramethylbutyl hydroperoxide. Organic peroxides with a one-minute half-life temperature of 100°C to 200°C are particularly preferred. In the specific examples described above, dicumyl peroxide and tert-butylcumyl peroxide are particularly preferred. It should be noted that in this invention, the "one-minute half-life temperature" is generally the value described in the "Organic Peroxide Catalogue, 10th Edition" of Nippon Oils & Fats Co., Ltd. Where not described, the value is obtained from thermal decomposition in the organic solvent, similar to the method described in the catalogue.

[0063] In the sealant material composition of the present invention, a crosslinking aid is preferably mixed in. A crosslinking aid is a compound that acts as a catalyst for the crosslinking reaction by being mixed with a crosslinking agent containing a sulfur component. By mixing the crosslinking agent and the crosslinking aid, the vulcanization rate can be accelerated, and the productivity of the sealant material composition can be improved. The mixing amount of the crosslinking aid is preferably more than 0 parts by mass and less than 1 part by mass relative to 100 parts by mass of the aforementioned rubber component, more preferably 0.1 to 0.9 parts by mass. By suppressing the mixing amount of the crosslinking aid in this way, it can act as a catalyst to promote the crosslinking reaction and suppress the deterioration (thermal deterioration) of the sealant material composition. If the mixing amount of the crosslinking aid is more than 1 part by mass, the effect of suppressing thermal deterioration cannot be sufficiently obtained. It should be noted that, as described above, the crosslinking aid acts as a catalyst for the crosslinking reaction by being mixed with a crosslinking agent containing a sulfur component. Therefore, even if it is coexisted with an organic peroxide instead of the sulfur component, it cannot achieve the effect of acting as a catalyst for the crosslinking reaction, and a large amount of the crosslinking aid must be used, thus promoting thermal deterioration.

[0064] The mixing amount of the crosslinking agent is preferably 50% to 400% by mass of the mixing amount of the aforementioned crosslinking aid, more preferably 100% to 200% by mass. By mixing the crosslinking agent and crosslinking aid in such a balanced manner, the catalytic function of the crosslinking aid can be effectively utilized, which is beneficial for balancing ensuring sealing and preventing sealant flow. If the mixing amount of the crosslinking agent is less than 50% by mass of the mixing amount of the crosslinking aid, the flowability decreases. If the mixing amount of the crosslinking agent exceeds 400% by mass of the mixing amount of the crosslinking aid, the resistance to degradation decreases.

[0065] Examples of crosslinking aids include compounds (vulcanization accelerators) based on sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine, aldehyde-amine, imidazoline, and xanthic acid. Among these, thiazole, thiuram, guanidine, and dithiocarbamate vulcanization accelerators are preferred. Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole and dibenzothiazole disulfide. Examples of thiuram-based vulcanization accelerators include tetramethylthiuram monosulfide and tetramethylthiuram disulfide. Examples of guanidine-based vulcanization accelerators include diphenylguanidine and di-o-tolylguanidine. Examples of dithiocarbamate-based vulcanization accelerators include sodium dimethyldithiocarbamate and sodium diethyldithiocarbamate. In this invention, thiazole-based or thiuram-based vulcanization accelerators are particularly preferred, as they can suppress deviations in the performance of the obtained sealant material composition.

[0066] It should be noted that, for convenience, there are cases where compounds that actually function as crosslinking agents, such as quinone dioxime, are referred to as crosslinking aids. However, the crosslinking aids of the present invention refer to compounds that function as catalysts in crosslinking reactions, such as those described above. Therefore, quinone dioxime does not meet the criteria for crosslinking aids of the present invention.

[0067] The sealant material composition of the present invention preferably contains a mixed liquid polymer. By mixing the liquid polymer in this way, the viscosity of the sealant material composition can be increased, thereby improving the sealing performance. The mixing amount of the liquid polymer is preferably 50 to 400 parts by weight, more preferably 70 to 200 parts by weight, relative to 100 parts by weight of the aforementioned rubber component. If the mixing amount of the liquid polymer is less than 50 parts by weight, the effect of increasing the viscosity of the sealant material composition may not be sufficiently obtained. If the mixing amount of the liquid polymer exceeds 400 parts by weight, the flow of the sealant cannot be adequately prevented.

[0068] As a liquid polymer, it is preferable to be able to co-crosslink with the rubber component (butyl rubber) in the sealant material composition. Examples include paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, polyisobutylene oil, aromatic oil, and polypropylene glycol. From the viewpoint of suppressing the low temperature dependence of the physical properties of the sealant material composition, thereby ensuring good sealing performance at low temperatures, paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, aromatic oil, and polypropylene glycol are preferred among these, with paraffin oil being particularly preferred. By using paraffin oil, it is advantageous to set the viscosity at each of the above temperatures to an appropriate range. Furthermore, the molecular weight of the liquid polymer is preferably 800 or more, more preferably 1000 or more, and even more preferably 1200 or more and 3000 or less. By using a liquid polymer with a high molecular weight in this way, it is possible to prevent oil from migrating from the sealant layer on the inner surface of the tire to the tire body and affecting the tire.

[0069] The present invention will be further described below through embodiments, but the scope of the present invention is not limited to these embodiments.

[0070] Example

[0071] Tires for Comparative Examples 1-2 and Examples 1-8 were manufactured, with a tire size of 235 / 40R18, and having... Figure 1 or Figure 2 The basic structure shown is used in a pneumatic tire with a sealant layer on the inner surface of the tread, for the thickness variation rate R. G Thickness change rate R G ', Width change rate R W Width change rate R W Viscosity η -30 Viscosity η0, viscosity η 50 Viscosity η 80 , ratio η0 / η 50 , compared to η -30 / η 80 The proportion of toluene-insoluble matter A, the presence or absence of auxiliary sheets, and the ratio of the area of ​​the auxiliary sheets to the surface area of ​​the sealant layer are set as described in Table 1.

[0072] Thickness change rate R G Based on the thickness G0 of the sealant layer at 0°C and the thickness G of the sealant layer at 50°C 50And calculated based on the following formula (1). Specifically, at each of the twelve equal divisions of the inner circumference of the tire, the equator position of the tire and three positions 10 mm inside the tire width direction from both ends of the sealant layer are respectively set as measurement points. At each measurement point, a needle with a diameter of 0.5 mm is vertically inserted into the sealant layer. When the tip of the needle reaches the interface between the sealant layer and the inner surface of the tire, the position of the needle corresponding to the surface of the sealant layer (the surface on the inner side of the tire cavity) is marked. The length from the tip of the needle pulled out of the sealant layer to the aforementioned mark (the thickness of the sealant layer) is measured. "Thickness of the sealant layer at 0°C G0" and "Thickness of the sealant layer at 50°C G0" are also measured. 50 "After setting the ambient temperature of the tires to their respective temperature conditions (0℃ or 50℃) and allowing them to stand for one hour, measurements were taken to determine G0 and G at each measurement point." 50 The difference (|G) 50 -G0|), the value of the measurement point with the largest difference is set as the "thickness change rate R". G ".

[0073] R G =(|G 50 -G0| / G0)×100 (1)

[0074] Thickness change rate R G 'Thickness G of the sealant layer based on -30℃' -30 And the thickness G of the sealant layer at 80℃ 80 And calculated based on the following formula (1'). Measurement conditions other than temperature, etc., are related to the aforementioned thickness change rate R. G same.

[0075] R G '=(|G 80 -G -30 | / G -30 )×100 (1')

[0076] Width change rate R W The width W0 of the sealant layer at 0°C and the width W of the sealant layer at 50°C 50 And calculate using the following formula (2). Specifically, the inner circumference of the tire is divided into twelve equal parts as measurement points. At each measurement point, the length (width of the sealant layer) between the two ends of the sealant layer along the tire width direction is measured, "width of the sealant layer W0 at 0°C" and "width of the sealant layer W at 50°C". 50 "After setting the ambient temperature of the tires to their respective temperature conditions (0℃ or 50℃) and letting them stand for one hour, the values ​​W0 and W at each measurement point were determined." 50 The difference (|W) 50 -W0|), set the value of the measurement point with the largest difference as "width change rate R" W ".

[0077] R W =(|W 50 -W0| / W0)×100 (2)

[0078] Width change rate R W 'Width W of the sealant layer based on -30℃' -30 and the width W of the sealant layer at 80℃ 80 And calculated based on the following formula (2'). Measurement conditions other than temperature, etc., are related to the aforementioned thickness change rate R. W same.

[0079] R W '=(|W 80 -W -30 | / W -30 )×100 (2')

[0080] Viscosity η -30 The viscosity of the sealant material at -30℃ is η0, and the viscosity of the sealant material at 0℃ is η0. 50 The viscosity of the sealant material at 50℃ is η. 80 The viscosity of the sealant material at 80℃ was measured using a rotational viscometer under various temperature conditions according to JIS K6833-1:2008.

[0081] The proportion of toluene-insoluble matter A [mass %] is calculated using the mass M2 [unit: g] of the toluene-insoluble matter remaining after the sealant material has been impregnated with toluene and left for one week, and the initial mass M1 [unit: g] of the sealant material before it has been impregnated with toluene, and by the following formula (3).

[0082] A = (M2 / M1) × 100 (3)

[0083] In any example, the width of the belt layer is set to 195 mm, the width of the sealant layer (width at 25°C) is set to 215 mm (1.10% of the width of the belt layer), and the thickness of the sealant layer (thickness at 25°C) is set to 3 mm.

[0084] For these test tires, the extrusion speed, processability, and sealing performance were evaluated using the following test methods, and the results are shown in Table 1.

[0085] Sealing

[0086] After each test tire was left to stand for 24 hours under the temperature conditions described later, it was mounted on a wheel with a rim size of 18×8.5J. Under an initial tire pressure of 250 kPa and a load of 8.5 kN, a 4.0 mm diameter nail was driven into the tire tread. The tire pressure was then measured after the nail was removed and the tire was left to stand for one hour under the temperature conditions described later. Four temperature conditions were set: -30℃, 0℃, 50℃, and 80℃, and tests were conducted under each of these conditions. It should be noted that the temperature conditions when driving in the nail were the same as those when the tire was left to stand before and after the nail was driven in. The evaluation results are expressed in four stages. It should be noted that an evaluation result of "3" or "4" indicates adequate sealing performance, while "4" indicates exceptionally excellent sealing performance.

[0087] 4: The air pressure after settling is above 240 kPa and below 250 kPa.

[0088] 3: The air pressure after settling is above 230 kPa and below 240 kPa.

[0089] 2: The air pressure after settling is above 200 kPa and below 230 kPa.

[0090] 1: The air pressure after settling is less than 200 kPa

[0091] sealant flowability

[0092] The test tire was assembled onto a wheel with a rim size of 18×8.5J and mounted on a drum testing machine. The air pressure was set to 220 kPa, the load to 8.5 kN, and the driving speed to 150 km / h for one hour. The flow state of the sealant after driving was investigated. For the evaluation results, a 20×40 grid of 5 mm squares was drawn on the surface of the sealant layer before driving. After driving, the number of deformed squares was counted. "3" indicates that the flow of sealant was completely not confirmed (0 deformed squares), "2" indicates that the number of deformed squares is less than 1 / 4 of the total, and "1" indicates that the number of deformed squares is more than 1 / 4 of the total.

[0093]

[0094] As shown in Table 1, the pneumatic tires of Examples 1-8 exhibited excellent sealing performance regardless of temperature conditions. Furthermore, the pneumatic tires of Examples 1-8 also demonstrated good flowability, with sealant flow suppressed after driving. In particular, the tires of Examples 1-5, which included an auxiliary sheet, showed virtually no sealant flow, demonstrating exceptionally excellent flowability. On the other hand, in Comparative Examples 1-2, the thickness change rate R... G and width change rate R WThe size was too large, thus failing to ensure adequate sealing and fluidity.

[0095] Explanation of reference numerals in the attached figures

[0096] 1: Fetal face;

[0097] 2: Side wall portion;

[0098] 3: Bead area;

[0099] 4: Body layer;

[0100] 5: Tire bead core;

[0101] 6: Tire sidewall core;

[0102] 7: Belt layer;

[0103] 8: Belt reinforcement layer;

[0104] 9: Inner lining layer;

[0105] 10: Sealant layer;

[0106] 11: Auxiliary film;

[0107] R1: Tread rubber layer;

[0108] R2: Sidewall rubber layer;

[0109] R3: Rim buffer rubber layer;

[0110] CL: Tire equator.

Claims

1. A pneumatic tire comprising: a tread portion extending in a circumferential direction of the tire to form an annular shape; a pair of sidewall portions disposed on both sides of the tread portion; and a pair of bead portions disposed inside the sidewall portions in a tire outer diameter direction, wherein a sealant layer made of an adhesive sealant material is provided at least on the inner surface of the tread portion, characterized in that... The adhesive sealant material is composed of a sealant material composition consisting of 0.1 to 40 parts by weight of a crosslinking agent mixed with 100 parts by weight of rubber component, wherein the crosslinking agent contains sulfur component but does not contain organic peroxide. When the thickness of the sealant layer at 0°C is defined as G0, and the thickness of the sealant layer at 50°C is defined as G... 50 The width of the sealant layer at 0°C is set as W0, and the width of the sealant layer at 50°C is set as W... 50 At that time, the thickness change rate R is expressed by the following formula (1). G For width changes of less than 3%, the following formula (2) represents the rate of change R. W The viscosity η0 of the adhesive sealant material at 0°C is less than 3%, and the viscosity η of the adhesive sealant material at 50°C is... 50 The ratio η0 / η 50 The viscosity η0 is 6.0 or less, the unit of the viscosity η0 is kPa·s, the unit of the viscosity η50 is kPa·s, and in the adhesive sealant material, the proportion A of toluene insoluble matter, expressed by the following formula (3), is 30% to 60% by mass. R G =(|G 50 -G0| / G0)×100(1) R W =(|W 50 -W0| / W0)×100(2), A = (M2 / M1) × 100 (3) In the formula, M2 is the mass of the toluene-insoluble residue remaining after the adhesive sealant material is immersed in toluene and left for one week, and its unit is g; M1 is the initial mass of the adhesive sealant material before it is immersed in toluene, and its unit is g.

2. The pneumatic tire according to claim 1, characterized in that, The adhesive sealant material has been cross-linked.

3. The pneumatic tire according to claim 1 or 2, characterized in that, The rubber component constituting the adhesive sealant material includes butyl rubber.

4. The pneumatic tire according to claim 1 or 2, characterized in that, An auxiliary sheet is provided to cover the surface of the sealant layer.

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